We propose to investigate the metabolism of trehalose in parasitic nematodes, using Ascaris as our experimental system. Trehalose and glucose are the two major low-molecular weight carbohydrates found in most parasitic nematodes; both storage and transport functions have been postulated for trehalose. Therefore, it is of interest to determine how trehalose fits into the overall carbohydrate metabolism of the worm. Isolation and characterization of the enzymes involved in the synthesis and degradation will be undertaken. The enzymes we propose to study are trehalose-P synthetase, trehalose-P phosphatase, and trehalase. The tissue distribution of these enzymes will also be examined. Properties of the enzymes in the different tissues will be studied to determine whether this system may be more important in some tissues than in others. Particular attention will be paid to those properties which may be of regulatory value in integrating trehalose into total carbohydrate metabolism. The sequential processes of degradation and synthesis of trehalose during embryogenesis offer a unique opportunity to study the regulation of an enzyme system during embryological differentiation. The trehalose-metabolizing enzymes will be assayed during development, and their activities correlated with the changing patterns of stored trehalose found in the egg. We propose studies to elucidate the mechanism(s) involved in the activation and suppression of this system.